Vincent Verweij
Vincent Verweij
Topics • How to measure forest health
• Natural and urban forests
• Threats
• Current data • Canopy
• Inventory
• Extrapolations
• Wildlife
• Future data • iTree Eco
• Summary
• What are we doing?
• What can you do?
• Questions
How do you measure forest health?
• Quantity
– Amount of trees
– Tree canopy cover
• Quality
– Diversity and structure
– Health/Disease
– Invasive Species
– Age distribution
– Soil condition
Comparing the health of natural and urban forests
• Natural:
– Community
– Interconnectedness
• Urban
– Individual trees
– Risk/benefit
– Resistance to stress
Threats to our urban forest
Storms
Invasive plants Deer pressure
Preventing regrowth
Poor practice
Pests and disease
Climate change Development
Current data
• Tree canopy: – 2008 Study, Virginia Tech
– 2011 Study, Vermont
• Tree inventory – 2003 inventory
– Champion trees
• Extrapolation from Casey trees iTree Eco study in DC:
• Wildlife supported by our urban forest
Tree Canopy
the layer of leaves, branches, and stems of trees that cover the ground when viewed from above.
At 40% tree canopy, we currently meet the American Forests recommended goal
Tree Canopy – Contiguous forests
Who owns our tree canopy?
Tree Canopy – County land
The majority of tree canopy is on private land, but we do manage some natural lands in parks
Total natural land: 349 Acres (2% of the County)
Arlington County: 240 Acres
NVRPA: 109 Acres
Natural Resource Conservation Areas: 129 Acres
Tree Canopy – Urban areas
Mixed ownership
Crystal City: 10.3%
Pentagon City: 18.5%
R-B Corridor: 22.2%
Columbia Pike: 34.6%
American Forests
recommends 15% targets for
central business districts, and
25% for urban residential.
Tree Canopy – Too much data
Owner Area
(Acres) %
Planting
Space
(Acre)
Planting
Space %
2008
UTC UTC %
Open
Planting
Space
(Acre)
Open
Planting
Space %
% of
County Notes
Public 5538 37.7 2724 49.2% 2035 36.7% 1147 20.7% 7.8%
County 1561 10.6 1187 76.0% 773 49.5% 454 29.1% 3.1%
NVRPA 138 0.9 124 90.0% 106 76.8% 20 14.5% 0.1%
State 11 0.1 4 32.7% 1 12.6% 3 27.3% 0.0%
Not statistically
significant
Right-of-Way 3180 21.6 870 27.4% 802 25.2% 467 14.7% 3.2% UTC overhangs roads
National Parks 648 4.4 539 83.2% 353 54.4% 203 31.3% 1.4%
Arlington Cemetery
not included
Private 9170 62.3 5892 64.3% 4314 47.0% 2215 24.2% 15.1%
UTC overhangs
buildings
Total 14708 100 8616 59% 6349 43% 3362 23%
Maximum UTC: 9711
Acres, 66%
Most of the open planting space is on private land. Our
maximum tree canopy could be 66%, unless we take out
roads and buildings
Tree Canopy change
Between the 2008 and 2011 studies, Arlington County went from 43% tree canopy to 40%.
These studies typically have less than 1% error
2003 Street tree inventory
• ~19,000 street trees
• Partially updated in 2008 and 2012
• Labor-intensive
4651
3513
1356 1066 858 763 759 688 555 550 458 435 348 344 341 331 294 274 240 215
2403
Species Composition
Champion tree inventory
• 105 Champion trees (County and state)
– 12 State champions, 44 listed co-championsPublic link to map can be found on http://gis.arlingtonva.us/gallery/index.html
Current Data: Extrapolation from other studies
• Casey Trees iTree Eco study, Washington, DC • iTree Eco measures the structural and environmental value of
trees in a community through random sampling.
• Results of DC Stats adapted to the size of Arlington • Approximately 1 Million trees
• $1.6 Billion Structural value
• Economic contribution of street trees – iTree Streets, with assumptions on tree locations
– 19,000 Street trees have $998,000 annual value in environmental services, such as energy reduction and carbon storage
Current Data: Wildlife Our urban forest provides food and shelter for
almost 200 birds species, 12 amphibians, 16
reptiles, 26 types of mammal, 28 dragonflies,
and 39 species of butterfly.
In summary: Some thoughts on our forest health • Quantity:
– At 40%, still at the target for our type of community
– Percentage is declining overall, though improving in urban areas
– More value should be given to preserving trees and forest
• Quality: – We see improving conditions for urban trees
– Need more information on species and age makeup
– Invasives and excessive deer browse are affecting our canopy negatively. Impact studies may be needed
– Soil compaction and climate change may cause longterm decline
– Continue to monitor for disease and use Integrated Pest Management
– Need improvement in connectivity between forests
What are we already doing? • Increased soil volumes for street trees and onsite
trees
• Going above and beyond requirements for tree canopy on county and APS projects
• Invasive plant control (193 Acres under treatment, of 458 acres planned to be treated)
• Restoration projects throughout the county
• Maximizing street trees on private projects, along with ensuring onsite tree canopy
• Credit for preserving trees
• Administrative Regulation 4.3
Future studies and work • Planned: 2016 iTree Eco study
• Potential other studies: – Impact of development
– Deer browse surveys
– Soil Profile rebuilding research
– Tree Canopy update (last one was in 2011)
– Mortality studies on planted trees
• Urban Forest Masterplan rewrite
What can you do where you live? • Maintain and protect your mature trees
• Plant a diversity of new native trees, where appropriate
• Remove non-native invasive vines
• Limit lawn area, where appropriate
• Cut back on fertilization
• Reduce compaction
• Advocate
Resources • iTree Eco study:
http://environment.arlingtonva.us/trees/2016-itree-eco-study/
• Arlington Forest health (Canopy study information): http://environment.arlingtonva.us/trees/how-arlington-rates-trees/
• Arlington county recommended trees: http://environment.arlingtonva.us/trees/plant-trees/recommended-trees/
• Ordinance on tree preservation: http://topics.arlingtonva.us/building/chesapeake-bay-preservation-ordinance/
• Native plants in Northern Virginia: http://www.plantnovanatives.org/
Questions? Vincent Verweij
[email protected] 703-228-1863
Natural Arlington Blog:
http://environment.arlingtonva.us/category/natural-arlington/
Arlington Forestry Facebook page:
Search “Arlington Forestry” on Facebook.
https://www.facebook.com/groups/271134212980703/